I think picking the fight was his way of trying to end the relationship with you because deep down, as he finally told you, he doesn’t like sick people. Maybe it reminds him of his own vurnerabilities, that it could just as easily be him. Or maybe it makes him mad that you betrayed him by getting sick. It seems he did it in such a hurtful way as to never get the friendship back. You did the right thing in at least trying to resolve issues with him, so now you know for sure this relationship can’t be fixed. It hurts to lose a long time friendship, but this is one that needs to be let go for good. Your mental health is more important than his issues with mental health.